Methods and apparatus for retaining gas turbine engine nozzle basesheets

ABSTRACT

A method for assembling a flap and seal system for a gas turbine engine exhaust nozzle including a plurality of backbone assemblies facilitates attaching a basesheet to a backbone. The method includes attaching an attachment system including at least one strap to a basesheet, and coupling the basesheet to a backbone using the attachment system strap.

GOVERNMENT RIGHTS STATEMENT

[0001] The United States Government has rights in this inventionpursuant to Contract No. F336957-99-D-2050.

BACKGROUND OF THE INVENTION

[0002] This invention relates generally to gas turbine engine exhaustnozzles and more particularly, to methods and apparatus for retainingbasesheet assemblies within gas turbine engine exhaust nozzles.

[0003] At least some known gas turbine engines include an exhaust nozzleincluding a variable geometry system. The variable geometry systemadjusts an area of the exhaust nozzle through the use of flaps andseals. The flaps define discrete sectors of the flowpath, and the sealsform the remaining flowpath between adjacent flaps. Because the exhaustnozzles are subjected to high temperatures and thermal gradients as aresult of hot combustion gases exiting the engine, the variable geometrysystems must maintain a coherent flowpath while shielding the structuralcomponents of the variable geometry system.

[0004] At least some known flap and seal systems consist of a backboneand a basesheet. The backbone secures the basesheet within the variablegeometry system. To facilitate extending a useful life at hightemperature operation, at least some known basesheets are fabricatedfrom non-metallic materials, such as ceramic matrix composite (CMC)materials.

[0005] At least some known basesheets are attached to the backbone usingmechanical fasteners, such as rivets or bolts. Over time, continuedthermal expansion may create local stress concentrations within thebolted and riveted joints. Furthermore, continued thermal cycling mayloosen such mechanical fasteners. Other known basesheets are attached tothe backbone with embedded attachments. Such attachments rely primarilyon an interlaminar tensile strength of the basesheet material to remainin place. Because such tensile strength may be a weakest load paththrough the basesheet, continued thermal cycling may loosen suchembedded attachments and induce potentially damaging stresses into thebasesheet.

BRIEF SUMMARY OF THE INVENTION

[0006] In one aspect, a method for assembling a flap and seal system fora gas turbine engine exhaust nozzle including a plurality of backboneassemblies is provided. The method comprises attaching an attachmentsystem including at least one strap to a basesheet, and coupling thebasesheet to a backbone using the attachment system strap.

[0007] In another aspect, an assembly for a gas turbine engine exhaustnozzle is provided. The assembly comprises a basesheet, a backbone, andan attachment sub-assembly. The attachment sub-assembly including atleast one strap attached to the basesheet and configured to couple thebasesheet to the backbone.

[0008] In a further aspect, a gas turbine engine is provided. The gasturbine engine comprises a variable engine exhaust nozzle including aflap and seal system coupled to the engine exhaust nozzle. The flap andseal system includes a basesheet, a backbone, and an attachmentassembly. The attachment assembly is configured to couple the basesheetto the backbone, includes at least one strap attached to the basesheetfor coupling the basesheet to the backbone.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a schematic illustration of a gas turbine engine; and

[0010]FIG. 2 is a perspective view of flap system that may be used withthe engine shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0011]FIG. 1 is a schematic illustration of a gas turbine engine 10including a fan assembly 12, a high pressure compressor 14, and acombustor 16. In one embodiment, engine 10 is a F414 engine availablefrom General Electric Company, Cincinnati, Ohio. Engine 10 also includesa high pressure turbine 18 and a low pressure turbine 20. Fan assembly12 and turbine 20 are coupled by a first shaft 24, and compressor 14 andturbine 18 are coupled by a second shaft 26.

[0012] In operation, air flows through fan assembly 12 and compressedair is supplied from fan assembly 12 to high pressure compressor 14. Thehighly compressed air is delivered to combustor 16. Airflow fromcombustor 16 drives rotating turbines 18 and 20 and exits gas turbineengine 10 through an exhaust system 28. Exhaust system 28 includes avariable geometry system 30.

[0013]FIG. 2 is a perspective view of a flap system 300 that may be usedwith the engine shown in FIG. 1. Flap system 300 is coupled to anexhaust nozzle, such as exhaust system 28 (shown in FIG. 1) tofacilitate shielding variable geometry system components from hightemperature combustion gases exiting the engine. More specifically, flapsystem 300 is coupled to the exhaust nozzle such that a flowpath side302 of flap system 300 is exposed to combustion gases exiting engine.Accordingly, flap system flowpath side 302 defines a portion of theflowpath through the nozzle.

[0014] Flap system 300 includes a plurality of backbones 304 andbasesheet assemblies 306 extending circumferentially within the engineexhaust nozzle. More specifically, basesheet assembly 306 is coupledwithin the engine exhaust nozzle by backbone 304, and has a leading edge310 and a trailing edge 312. Basesheet assembly leading and trailingedges 310 and 312, respectively, are coupled together by a pair of sideedges 314 and 316. In the exemplary embodiment, side edges 314 and 316converge to an apex 318 defined at basesheet assembly trailing edge 312.In the exemplary embodiment, side edges 314 and 316 are substantiallyparallel, and leading edge 310 is substantially perpendicular withrespect to side edges 314 and 316. In an alternative embodiment, flapsystem 300 includes basesheet assemblies 306 and side edges 314 and 316are non-parallel.

[0015] Flap system 300 also includes an attachment assembly 322 used tosecure each basesheet assembly 306 to a respective backbone 304.Alternatively, attachment assembly 322 may be used to secure anybasesheet assembly to backbone 304. In the exemplary embodiment,basesheet assembly 306 includes a unitary body 324 having flowpath side302 and a back side 328. Attachment assembly 322 is coupled to body backside 328. More specifically, attachment assembly 322 includes aplurality of straps 330 and at least one mounting tab 332. Straps 330are attached to body back side 328 and include a hanger portion 342 andan attachment portion 340. In the exemplary embodiment, each hangerportion 342 extends between adjacent attachment portions 340.

[0016] Straps 330 are spaced axially along body back side 328 betweenbasesheet assembly leading and trailing edges 310 and 312, respectively.In the exemplary embodiment, straps 330 are arranged in pairs that areaxially aligned adjacent opposite side edges 314 and 316 of basesheetassembly 306. Accordingly, in the exemplary embodiment, basesheetassembly 306 includes four pairs of straps 330. It should be noted thatthe number of straps 330 and the relative position of straps 330 withrespect to basesheet assembly 306 are variable.

[0017] Straps 330 are securely attached to body back side 328 byattachment portions 340 which contact body back side 328, such thatstrap hanger portions 342 are not in contact with body back side 328.Rather, strap hanger portions 342 extend a distance 344 from body backside 328 and define a slot 346 that extends between a respective straphanger portion 342 and body back side 328. In the exemplary embodiment,each strap hanger portion 342 extends an identical distance 344 frombody back side 328. Alternatively, each strap hanger portion 342 extendsa different distance 344 from body back side 328. Each slot 346 has awidth 348 extending between attachment portions 342. Slot widths 348 arevariably selected based on backbone 304. In the exemplary embodiment,each strap 330 is substantially H-shaped. In another embodiment, straps330 have non-substantially H-shaped cross-sectional profiles.

[0018] Attachment assembly mounting tab 332 is positioned along acenterline 350 of basesheet assembly 304 that extends between leadingand trailing edges 310 and 312, respectively. More specifically,mounting tab 332 is attached to basesheet assembly body back side 328adjacent basesheet assembly trailing edge 312. Mounting tab 332 iscontoured and includes an attachment portion 352 and a hanger portion354 extending from portion 352. Mounting tab attachment portion 352 issecurely attached to basesheet assembly 306 such that mounting tabattachment portion 352 is substantially flush against body back side 328while hanger portion 354 remains a distance 356 from body back side 328.

[0019] Basesheet assembly 306 also includes an opening 358 extendingthrough basesheet assembly 306 between flowpath and back sides 326 and302. Opening 358 is sized to receive a fastener (not shown) therethroughfor securely coupling basesheet assembly 306 to backbone 304.

[0020] Backbone 304 includes a body 360 extending axially between an aftend 362 and a leading end 364. Backbone body 360 includes a plurality ofattachment arms 370 spaced axially along body 360 between leading andaft ends 364 and 362, respectively. Arms 370 extend substantiallyperpendicularly from body 360 and each includes a respective hangerbracket 372. In the exemplary embodiment, backbone arms 370 are arrangedin pairs, such that opposing arms 370 within each pair extend outwardlyfrom body 360 in opposite directions. Furthermore, in the exemplaryembodiment, arms 370 are substantially co-planar.

[0021] Each hanger bracket 372 extends outwardly from each respectivebackbone arm 370 towards backbone body aft end 362. More specifically,each hanger bracket 372 extends substantially perpendicularly from atrailing edge side 374 of each arm 370. In the exemplary embodiment,hanger brackets 372 are identical. Alternatively, backbone 304 includesa plurality of different hanger brackets 372. Each hanger bracket 372has a width 376 that is slightly smaller than each corresponding straphanger portion slot width 348. Accordingly, each respective attachmentassembly strap hanger portion slot 346 is sized to receive acorresponding respective backbone hanger bracket 372 therethrough.

[0022] Backbone aft end 362 includes a hanger flange 380 for couplingbackbone aft end 362 with basesheet mounting tab 332. More specifically,hanger flange 380 is sized to be received between mounting tab hangerportion 354 and basesheet assembly body back side 328 when hanger flange380 is coupled with mounting tab 332.

[0023] During assembly of flap system 300, initially attachment assembly322 is attached to basesheet assembly 306 as described above. Eachbasesheet assembly 306 is then coupled to a respective backbone 304using attachment assembly 322. More specifically, basesheet assembly 306is initially positioned such that attachment assembly 322 and basesheetassembly back side 328 are adjacent a flowpath side 390 of backbone 304,and such that backbone 304 is substantially centered between basesheetassembly sides 314 and 316.

[0024] Basesheet assembly 306 is then translated with respect tobackbone 302 such that basesheet assembly 306 is shifted towardsbackbone leading end 364. In an alternative embodiment, basesheetassembly 306 is shifted towards backbone aft end 362 during assembly offlap system 300. As basesheet assembly 306 is shifted, each respectivebackbone hanger bracket 372 is received within a corresponding basesheetassembly strap hanger portion 340. Furthermore, as hanger brackets 372are extended through basesheet assembly strap hanger portion slots 346,backbone trailing end hanger flange 380 is received within basesheetassembly mounting tab 332, such that basesheet assembly 306 is coupledto backbone 304. Basesheet assembly 306 is then securely coupled tobackbone 304 by the fastener extending through basesheet assemblyopening 358.

[0025] During operation, as basesheet assembly 306 is exposed to hotcombustion gases exiting the engine, backbone hook brackets 372 permitattachment assembly 322 and basesheet assembly 306 to thermally expandrelative to backbone 304 while facilitating reducing thermal stressesinduced between basesheet assembly 306 and backbone 304. Morespecifically, attachment assembly 322 facilitates thermal growthdifferences between backbone 304 and basesheet assembly 306.Furthermore, attachment assembly 322 facilitates reducing assembly costsof flap system 300.

[0026] In the exemplary embodiments described herein, an attachmentsystem coupling a divergent flap backbone and a divergent flap basesheethas been illustrated. However, the attachment techniques describedherein can be applied to a similarly constructed convergent flapbackbone and convergent flap basesheet. Additionally, the attachmenttechniques described herein may be used to secure a convergent ordivergent seal basesheet to a respective convergent or divergent sealbackbone.

[0027] The above-described flap and seal system is cost-effective andhighly reliable. The flap and seal system includes a basesheet assemblyincluding an attachment assembly that couples the basesheet assembly tothe backbone. The attachment assembly includes a plurality of strapsthat receive a plurality of corresponding backbone hanger brackets. As aresult, the attachment assembly facilitates reducing thermal stressesbetween the basesheet assembly and the backbone in a cost-effective andreliable manner.

[0028] While the invention has been described in terms of variousspecific embodiments, those skilled in the art will recognize that theinvention can be practiced with modification within the spirit and scopeof the claims.

What is claimed is:
 1. A method for assembling a flap and seal systemfor a gas turbine engine exhaust nozzle including a plurality ofbackbone assemblies, said method comprising: attaching an attachmentsystem including at least one strap to a basesheet; and coupling thebasesheet to a backbone using the attachment system strap.
 2. A methodin accordance with claim 1 wherein the basesheet includes a flowside andan opposite back side, attaching an attachment system furthercomprising: attaching a plurality of straps to the basesheet; andattaching at least one strap to the basesheet back side.
 3. A method inaccordance with claim 1 wherein coupling the basesheet to a backbonefurther comprises coupling the basesheet to the backbone such that eachattachment system strap receives a hook extending from the backbonetherethrough.
 4. A method in accordance with claim 1 wherein couplingthe basesheet to a backbone further comprises coupling the basesheet tothe backbone using a mounting tab extending from the basesheet.
 5. Amethod in accordance with claim 1 wherein coupling the basesheet to abackbone further comprises orienting the basesheet relative to thebackbone with the attachment system.
 6. An assembly for a gas turbineengine exhaust nozzle, said assembly comprising a basesheet; a backbone;and an attachment sub-assembly comprising at least one strap attached tosaid basesheet and configured to couple said basesheet to said backbone.7. An assembly in accordance with claim 6 wherein said basesheetcomprises a flowpath side and an opposite back side, said attachmentsub-assembly extending from said basesheet back side.
 8. An assembly inaccordance with claim 6 wherein said basesheet comprises a flowpath sideand an opposite back side, said attachment sub-assembly furthercomprising a plurality of straps extending from said basesheet back sideand configured to couple said basesheet to said backbone.
 9. An assemblyin accordance with claim 6 wherein said backbone comprises at least onehook, said attachment sub-assembly strap configured to receive saidbackbone hook therethrough.
 10. An assembly in accordance with claim 6wherein said backbone comprises a plurality of hooks, said attachmentsub-assembly further comprising a plurality of straps, each said strapconfigured to receive a respective backbone hook therethrough.
 11. Anassembly in accordance with claim 6 wherein said basesheet furthercomprises at least one opening extending therethrough, said basesheetopening configured to receive a fastener therethrough for securing saidbasesheet to said backbone.
 12. An assembly in accordance with claim 6wherein said attachment sub-assembly further comprises a mounting tabattached to said basesheet and configured to couple said basesheet tosaid backbone.
 13. An assembly in accordance with claim 6 wherein saidattachment sub-assembly further configured to orient said basesheetrelative to said backbone.
 14. A gas turbine engine comprising avariable engine exhaust nozzle comprising a flap and seal system coupledto said engine exhaust nozzle, said flap and seal system comprising abasesheet, a backbone, and an attachment assembly configured to couplesaid basesheet to said backbone, said attachment assembly comprising atleast one strap attached to said basesheet for coupling said basesheetto said backbone.
 15. A gas turbine engine in accordance with claim 14wherein said flap and seal system basesheet comprises a flowpath sideand an opposite back side, said attachment assembly configured to attachsaid basesheet to said backbone such that said basesheet back sidebetween said basesheet flowpath side and said backbone.
 16. A gasturbine engine in accordance with claim 15 wherein said backbonecomprises at least one hook, said attachment assembly at least one strapconfigured to receive said at least one hook therethrough.
 17. A gasturbine engine in accordance with claim 15 wherein said attachmentassembly further comprises at least one mounting tab attached to saidbasesheet for coupling said basesheet to said backbone.
 18. A gasturbine engine in accordance with claim 15 wherein said attachmentassembly further configured to orient said basesheet with respect tosaid backbone.
 19. A gas turbine engine in accordance with claim15wherein said attachment assembly further comprises a plurality ofstraps attached to said basesheet.
 20. A gas turbine engine inaccordance with claim 15 wherein said backbone comprises a plurality ofhooks configured to couple to said basesheet.